I have been following and using Pluto home since version 2.038.Can someone tell me the differences (primarily the features) between Linux MCE - Plutohome and The commercial product Einstein from Monster.

The feature set is essentially the same for Pluto and LinuxMCE. The different platforms have highlighted some -shall we say- cross-platform bugs. But the functions are the same. Monster's Einstein system is not shipping so its not possible to comment in detail, but Einstein seems to have the same feature set. It may have some different components being a commercial product, including some software that isn't open source. They have promised shipping later this year but you never know until it has shipped.

I don't know of any other commercial products based on this yet. They are assured to be pretty expensive since the vendors are expected to make them work so the support is a costly requirement. However I think there is an opportunity for someone to offer a package of known good hardware with the software for the DIY/Hobbiest to work from.